The present invention relates to a new and distinct clonal rootstock for English walnut (Juglans regia) that has been denominated varietally as ‘RX1’, and more particularly to such a walnut rootstock that has reduced susceptibility to cankering by Phytophthora (Phytophthora citricola), and that further is easily clonally propagated by micropropagation.
It has long been recognized that Phytophthora root and crown rots are some of the most serious diseases of walnut worldwide. In California, Phytophthora citricola and P. cinnamomi are recognized as the most virulent species of the fungus, but P. citricola is more widespread. The rootstock of the present invention, ‘RX1’, has been identified as being more resistant to P. citricola than other available clonal walnut (Juglans) rootstocks.